1. Field of the Invention
The present invention relates to an ink-jet recording head and a method of manufacturing the same. More particularly, the present invention relates to an ink-jet recording head that jets ink particles through nozzle holes by changing the pressure of pressure chambers by deformations of pressure producing devices and a method of manufacturing such an ink-jet recording head.
2. Description of the Related Art
Generally, the ink-jet recording apparatus has a recording head provided with a plurality of nozzle holes arranged in a row, a scanning mechanism for moving a carriage supporting the recording head thereon in a scanning direction parallel to the width of a recording medium, such as a recording sheet, and a sheet feed mechanism for feeding a recording sheet in a feed direction parallel to the length of the recording sheet.
The recording head has a head structure provided with pressure chambers and nozzle holes respectively communicated with the pressure chambers, and pressure producing devices for changing the pressure of the ink contained in the pressure chambers. Ink particles are jetted through each nozzle hole by applying a driving pulse to the pressure producing device to change the pressure of the ink contained in the pressure chamber.
The scanning mechanism moves the carriage supporting the recording head in the scanning direction for a recording operation. During the recording operation, the recording head jets ink particles at points of time specified by dot pattern data. Upon the arrival of the recording head at the terminal point of a scanning range, the scanning mechanism returns the recording head to a starting point of the scanning range and the sheet feed mechanism moves the recording medium in the feed direction. Then, the scanning mechanism starts moving the carriage in the scanning direction and the recording head jets ink particles while the same is moved in the scanning direction. The recording head may be driven for printing during only a forward travel or may be driven for printing during both a forward travel and a return travel. These operations are repeated according to dot pattern data to record an image on the recording sheet.
Some ink-jet recording apparatus applies selectively a plurality of kinds of driving pulse of different waveforms produced from a common driving signal of a predetermined waveform to a recording head to jet ink particles of different kinds, such as ink particles respectively having different particle sizes. The period of the common driving signal, i.e., driving period, determines the printing speed of the recording apparatus.
FIG. 30 is an enlarged fragmentary sectional view of a recording head included in an ink-jet recording apparatus and FIG. 31 is an enlarged sectional view of pressure chambers and portions around the pressure chambers of the recording head shown in FIG. 30. As shown in FIGS. 30 and 31, a recording head 50 has a flexible sheet 53, a plate-shaped member 52 having partition walls 51 and attached to the front surface of the flexible sheet 53, and a plate-shaped member 55 having a plurality of lands 54 and attached to the back surface of the flexible sheet 53.
The partition walls 51 define a plurality of pressure chambers 56, a plurality of ink inlet passages 57 and common ink storage chambers 58. The pressure chambers 56 communicate with the common ink storage chambers 58 by means of the ink inlet passages 57, respectively. The lands 54 correspond to the pressure chambers 56, respectively.
The extremities of pressure producing devices 59 are in contact with the lands 54, respectively. The pressure producing device 59 includes a piezoelectric vibrator of a longitudinal vibration mode having a laminated piezoelectric element. The pressure producing devices 59 are attached to a fixed plate 60 fixed to a case 61.
Portions of the flexible sheet 53 around the lands 54 serve as elastic, deformable parts 63 capable of being elastically deformed by a deformation of the pressure producing devices 59.
A nozzle plate 64 is bonded to the front surface of the plate-shaped member 52. The nozzle plate 64 is provided with a plurality of nozzle holes 65 respectively connected to the pressure chambers 56.
The plurality of nozzle holes 65 are arranged along the feed direction on the recording head 50 at intervals corresponding to predetermined pitches that defines a dot density.
The extremity of an ink supply pipe 66 extended through the case 61, the plate-shaped member 55 and the flexible sheet 53 is connected to the common ink storage chamber 58 to supply the ink into the common ink storage chamber 58.
When manufacturing the known ink-jet recording head shown in FIGS. 30 and 31, a flat plate for forming the plate-shaped member 55 is attached to the back surface of the flexible sheet 53, and the lands 54 of the flat plate are formed on the flexible sheet 53 by etching the flat plate.
On the other hand, the plate-shaped member 52 provided with the partition walls 51 is bonded to the front surface of the flexible sheet 53 with an adhesive. Therefore, as shown in FIG. 32, it sometimes occurs that part 67 of the adhesive spreads into the pressure chamber 56 and the ink inlet port 57.
If the part 67 of the adhesive spreads into the pressure chamber 56 and the ink inlet port 57, pressure applied to the flexible sheet 53 cannot be satisfactorily transmitted to the pressure chamber 56 due to the deterioration of the flexibility of the flexible sheet 53 by the detrimental effect of the adhesive on the flexible sheet 53. Portions of the flexible sheet 53 corresponding to the different pressure chambers 56 have different deforming properties, respectively. As a result, the nozzle holes 65 have different ink jetting characteristics, respectively.
When bonding the plate-shaped member 52 provided with the partition walls 51 to the flexible sheet 53, it is difficult to bond the plate-shaped member 52 to the flexible sheet 53 so that the pressure chambers 56 are formed accurately in correct positional relation to the lands 54. Consequently, pressure cannot be properly applied to the pressure chambers. Portions of the flexible sheet 53 corresponding to the plurality of pressure chambers 56 are deformed differently. As a result, the nozzle holes 65 have different ink jetting characteristics, respectively.
When manufacturing the known recording head, portions of the plate-shaped member 52 having the partition walls 51 are removed by etching to form grooves for forming the ink inlet passages 57 before bonding the plate-shaped member 52 to the flexible sheet 53. If the portions of the plate-shaped member 52 are etched unequally and the grooves are formed different depths, respectively, the ink inlet passages 57 have different sectional areas, respectively. Consequently, pressure cannot be satisfactorily transmitted to the pressure chambers 56. The portions of the flexible sheet 53 respectively corresponding the plurality of pressure chambers 56 are deformed differently. As a result, the nozzle openings have different ink jetting characteristics, respectively.
Generally, as shown in FIGS. 33 and 34, an ink-jet recording head (hereinafter, referred to simply as “recording head”) employing pressure producing devices each including a piezoelectric vibrator of a longitudinal vibration mode has a passage unit 301 provided with a plurality of nozzle holes 308 and a plurality of pressure chambers 307, and a case 302 containing piezoelectric vibrators 306. The passage unit 301 is attached to the case 302.
The passage unit 301 is formed by superposing a nozzle plate 303 provided with the nozzle holes 303 arranged in rows, a passage plate 304 provided with a plurality of pressure chambers 307 respectively connected to the nozzle holes 308, and a vibrating plate 305 attached to the lower surface of the passage plate 304 so as to cover the lower open ends of the pressure chambers 307. The passage plate 304 is provided with ink storage chambers 309 connected to the pressure chambers 307 by ink inlet passages 310.
The case 302 is formed of a synthetic resin and has spaces 312 extending between the upper and the lower surface thereof. The piezoelectric vibrators 306 are contained in the spaces 312. The piezoelectric vibrators 306 have back ends fixed to base plates 311 attached to the case 302 and front ends fixed to lands 305A formed on the lower surface of the vibrating plate 305.
A driving signal produced by a 314 is transmitted through a flexible wiring plate 313 to the corresponding piezoelectric vibrator 306 to vibrate the piezoelectric vibrator longitudinally. Consequently, the land 305A of the vibrating plate 305 is vibrated to change the pressure in the pressure chamber 307, and thereby the ink contained in the pressure chamber 307 is jetted in ink particles through the nozzle holes 308. In FIG. 33, indicated as 315 are ink supply ports through which the ink is supplied to the ink storage chambers 309.
The passage plate 304 of the passage unit 301 is a plate formed by subjecting a single-crystal silicon substrate to an anisotropic etching process, such as that disclosed in JP-A No. Hei 9-123448, or an electroformed plate formed on a pattern by an electroforming process and removed from the pattern, such as those disclosed in JP-A No. Hei 6-305142 or Hei 9-300635.
When processing a single-crystal silicon substrate by an anisotropic etching process to form the passage plate 304 provided with the pressure chambers 307 and the ink inlet passages 310, the depth of the ink inlet passage 310 is controlled by calculating the etching time necessary to etch the layer in a desired depth. It is difficult to achieve the accurate control of the depth of the ink inlet passages 310 by such a method and there is a limit to the improvement of the accuracy of the depth of the ink inlet passages 310. When the passage plate 304 is formed by processing a photosensitive resin plate, a partition wall between the adjacent pressure chambers 307 is liable to be deformed by pressure applied to one of the adjacent pressure chambers 307 and crosstalk between the adjacent pressure chambers 307 occurs if the pressure chambers 307 are arranged in a high density because the photosensitive resin, as compared with a metal or silicon, has a low rigidity and, therefore, it is impossible to arrange the nozzle holes 308 in a high density. When the passage plate 304 is an electroformed plate, the passage plate 304 has a low dimensional accuracy because the electroformed plate is liable to be warped when removing the same from the pattern and the dimensional accuracy of the electroformed plate is liable to be reduced. The electroformed plate needs an additional process for removing the electroformed plate from the pattern, which is one of factors of cost increases.
In the recording head, the pressure chambers 307, the ink storage chambers 309 and the ink inlet passages 310 are formed in the single passage plate 304. Therefore, the passage plate 304 must have an area sufficient for arranging the pressure chambers 307, the ink storage chambers 309 and the ink inlet passages 310 thereon, and the miniaturization of the recording head is limited by the passage plate 304. Since the recording head employs the piezoelectric vibrators 306 of the longitudinal vibration mode, the passage unit 301 is liable to be deformed by the vibrations of the piezoelectric vibrators 306 and crosstalk is liable to occur. Therefore, the rigidity of the passage unit 301 must be increased to the highest possible extent, which places a restriction on the miniaturization of the recording head.
The passage plate 304 of the conventional recording head is a plate formed by subjecting a single-crystal silicon substrate to an anisotropic etching process, a plate formed by processing a photosensitive resin plate or an electroformed plate. The depth of the passages of the passage plate 304 formed by subjecting a single-crystal silicon substrate to an anisotropic etching process is controlled by calculating the etching time. Therefore it is difficult to form the passages accurately in a desired depth, which is a restriction on accuracy improvement. When the passage plate 304 is formed by processing a photosensitive resin plate, the partition wall between the adjacent pressure chambers 307 is liable to be deformed and crosstalk between the adjacent pressure chambers 307 occurs if the pressure chambers 307 are arranged in a high density because the photosensitive resin has a low rigidity and, therefore, it is impossible to arrange the nozzle holes 308 in a high density. When the passage plate 304 is an electroformed plate, the passage plate 304 has a low dimensional accuracy because the electroformed plate is liable to be warped when removing the same from the pattern and the dimensional accuracy of the electroformed plate is liable to be reduced. The electroformed plates needs an additional process for removing the electroformed plate from the pattern, which is one of factors of cost increases.